Optical validation data were collected using a Tethered Optical Assessment Device (TOAD), an underwater
sled equipped with an underwater digital video camera and lights. Data were collected on Penguin Bank on the southwest
coast of Molokai in the main Hawaiian Islands to support Benthic Habitat Mapping efforts.

Purpose:

This data provides optical observations that will be correlated with bathymetry and acoustic backscatter
imagery to develop a benthic habitat map of Molokai. Refer to supplemental information for description of instrument
and survey.

Supplemental_Information:

Molokai, formed from two extinct volcanoes, covers an area of 673 sq. km and reaches 1515 m
at its highest point. Generally situated between Maui and Oahu at 21 degrees 08'N, 157 degrees 00' W, the island has 142 km of
shoreline and an estimated 998 sq. km of reef (Hawaii Coral Reef Network). The island is one the four members of
the Maui Group (also including Maui, Lanai and Kahoolawe), situated together on a shallow, submerged bank. In the
recent geological past, the islands formed a single land mass (Maui Nui) during periods of lowered sea levels. Like
all of the main Hawaiian islands, it is considered a high island and contributes significant nutrient and sediment
runoff to coastal waters. Molokai's human population was counted at 6,717 in 1990, mostly scattered around the
island. There are no designated marine protected areas around Molokai, although the Hawaiian Islands Humpback Whale
National Marine Sanctuary spans 3642 sq. km of the waters among and around the Maui Group. Penguin Bank is a flat-topped
feature with a surface area of 1015 sq. km that extends from the west coast of Molokai approximately 70 km to the
southwest.
Optical validation data were collected using the Tethered Optical Assessment Device (TOAD), a sled equipped with
underwater video camera and lights. These data are used to provide ground-truth validation that for benthic habitat
maps based on multibeam echosounder surveys. A limited number of camera sled tows were conducted, to further
investigate specific features identified during multibeam surveying. The camera sled was deployed from lower arm
of the starboard J-frame on the NOAA Ship Hi'ialakai. At each station the ship was positioned with the wind on the
starboard side and drifted downwind; occasional light turns were applied to the ship's screws if necessary to
reduce the ship's motion. The TOAD was lowered slowly to the bottom by the deck crew. The operator monitored a
live video feed from the camera and began recording data on two video tape recorders. When the camera reached
bottom the deck crew was notified by radio to stop lowering. The operator continued to monitor the vehicle and
provided commands to raise or lower it to keep the camera just above the bottom.

Equipment Description: The TOAD was deployed from the lower arm of the vessel's J-frame. The TOAD is a camera
sled based on the Guildline MiniBat model 8820 tow body. The frame has been extensively modified from its original
configuration and was configured with a single ROS model 54-00100-13 color underwater video camera and two 500 W
DeepSea Power & Light model 710-0400601 underwater lights mounted on the original sled frame. The MiniBat pressure
sensor and wing controller was also mounted on the frame but no wings were installed. Cable between the sled and
the surface consisted of an underwater electrical cable (cable 1, blue in color) with a separate load-bearing line
to support the sled frame. The electrical cable was clipped to the line at regular intervals upon deployment and
removed upon recovery. The load-bearing line was led to the starboard capstan on the aft deck. All TOAD surface
components were located in the Dry Lab in an equipment rack on the after bulkhead.

Data Files: Video data were recorded on two video tape recorders. The position of the camera sled was recorded
using Hypack Max version 02.012a survey software.

File naming convention: Each tow is given a name consisting of a 3-letter designator for the island area followed
by a two-digit year and three-digit tow number. For example, during HI0504 the first tow was called MOL05000.
Video tape labels and paper log forms are all annotated with the tow name. Data files recorded in Hypack software
followed their CHS filename format consisting of the year, the first two letters of the platform name, the Julian
date, and the hour and minute in which the file was started. For example, a file collected on July 18, 2005 (Julian
date 199) aboard the Hi'ialakai starting at time 1935 would be 2005HI1991935.

Time Correlation: All times are based on UTC. Three clocks were manually synchronized prior to starting data
collection; the clock in the video character generator that was used to annotate the video tape, in one of the
video cassette recorders, and in the computer running the Hypack Max software. These clocks were set to UTC at the
beginning of each evening's operations.

The horizontal position accuracy for the camera sled position is 50 meters.
There are two primary sources of this error. The ship's positioning is based on GPS SPS, often called standalone
or non-differential GPS positioning. SPS has a measured accuracy of under 5 meters. The position of the GPS
antenna is translocated to that of the tow block from which the camera is deployed. The difference between the
tow block and the antenna is about 14 meters. The camera sled position is based a layback calculation that use
ship's course, the amount of cable out and the camera sled depth to develop an estimate of the camera sled position.
The amount of cable deployed is manually entered by the operator during a given camera tow.

Lineage:

Process_Step:

Process_Description:

After a tow was completed the video tape data was reviewed by spot-checking the master and
backup tape to verify that data were recorded.
Raw data files recorded using Hypack Max software include time, horizontal position, and ship's heading information
were copied from the acquisition computer to the data archive.

Tow-specific metadata were recorded in the data archive in the same location as the raw data, in a spreadsheet
that was then referred to in creating metadata records of each island where data were collected during the cruise.
Raw data files were exported as comma-delimited text files which were then imported into ArcGIS v8.3 and saved
as shapefiles.

These data are not to be used for navigational purposes. NOAA makes no warranty regarding
these data, expressed or implied, nor does the fact of distribution constitute such a warranty. NOAA cannot assume
liability for any damages caused by any errors or omissions in these data, nor as a result of the failure of these
data to function on a particular system.

Standard_Order_Process:

Digital_Form:

Digital_Transfer_Information:

Format_Name: ASCII

Format_Information_Content:

Each comma-delimited record contains year, day of year, time, latitude, longitude,
velocity north and east, water column depth, vehicle depth, layback, and wing angle. For this data set the
fields for vehicle depth and wing angle do not contain useful data.
List of navigation files:
2005HI180838.RAW
2005HI1802005.RAW
2005HI1802143.RAW
2005HI1802209.RAW
2005HI1802257.RAW